13 October 2008 Correction of atmospheric scattering effects in space-based observations of methane and carbon dioxide: model study for synthesized GOSAT spectra
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Proceedings Volume 7107, Remote Sensing of Clouds and the Atmosphere XIII; 71070U (2008); doi: 10.1117/12.799712
Event: SPIE Remote Sensing, 2008, Cardiff, Wales, United Kingdom
Abstract
This paper concerns development of a new retrieval algorithm for the processing of the Greenhouse gases Observing SATellite (GOSAT) data. GOSAT is scheduled to be launched in 2009 to monitor column amounts of CO2 and CH4. A nadir-looking Fourier-Transform Spectrometer (FTS) of Short Wavelength Infrared (SWIR, 1.6 microns and 2 microns) and 0.76 microns oxygen A-band regions are mounted on GOSAT. We focus on the methane retrievals from 1.67 μm spectral band under conditions of strong optical path modification due to atmospheric scattering. First, the algorithm of spectral channel selection is proposed to reduce the effects of uncertainties in water vapor content and solar spectrum. Two techniques for the atmospheric scattering correction are compared: one uses CO2 as a proxy gas; the second is based on the simple parameterization of photon path-length probability density function (PPDF). The latter technique includes the following steps: estimation of PPDF parameters from radiance spectra in the O2 A-band and 2.0 -μm CO2 band, the necessary correction to use these estimated parameters in the 1.58-μm CO2 and 1.67-μm CH4 bands; and, finally, CO2 and methane retrievals. Both approaches were verified by numerical simulations using an independent radiative transfer approach to produce radiance spectra expected for the GOSAT sensor. The accuracy of the retrievals in the presence of aerosols and cirrus cloud is discussed.
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Andrey Bril, Sergey Oshchepkov, Tatsuya Yokota, "Correction of atmospheric scattering effects in space-based observations of methane and carbon dioxide: model study for synthesized GOSAT spectra", Proc. SPIE 7107, Remote Sensing of Clouds and the Atmosphere XIII, 71070U (13 October 2008); doi: 10.1117/12.799712; https://doi.org/10.1117/12.799712
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KEYWORDS
Atmospheric modeling

Carbon dioxide

Methane

Atmospheric corrections

Scattering

Algorithm development

Atmospheric optics

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